Does a genset still make sense?

[malbert73]

Originally Posted by s/v Jedi

That’s not what I see on smaller boats with large arrays: they do just fine. There’s a whole range of them on YouTube posting videos with ocean crossings, bad weather etc. with large arrays and they do great.



Evidence shows that large arrays do fine.

Ah yes, YouTube proof🤣.

Let me flip this- what is “doing great”?whenever I’ve sailed upwind with out my canvas dodger/Bimini, the boat has another gear in terms of pointing and speed.
But I still cruise with canvas because it’s worth it and my dermatologist insists I need to

I’m not saying a large solar array isn’t worth it for some. But to say it’s got no effect is to deny basic physics. I think from your posts here you’re a pretty scientific guy like me so I imagine you’re just being provocative

There are no absolutes, just relative choices.
I’d rather keep my genset which has no windage. Others would rather have a huge array of renewables and take a performance hit. I’m sure you know this

[Icarus]

Originally Posted by pwillems

I have always read that the purpose behind installing a standalone genset rather than just using the main engine to charge batteries is due to the inefficiencies of running a diesel engine with only the light load from the alternator. This makes sense, and I would agree. But, these days, it is quite easy to get hold of some very large alternators and very large inverters, so I am not sure it always makes all that much sense anymore.

Let's say a small catamaran owner has 2 * 20hp and a decent lithium bank that will happily accept high charge rates. A 400amp/12v alternator uses ~16hp (1 hp per 25 amps). At the full 400 amps output, that engine is at over 75% working load. Taking into account heat derating and other inefficiencies, the engine is still getting a pretty good workout for the entire duration of the charge.

Of course, you wouldn't want that alternator putting out its full charge when you actually need that engine to push the boat into some challenging seas, but that is easily managed with a clever regulator, or even a potentiometer if required.

My 1000W Honda quite easily runs my 60A/240V AC Enerdrive charger... If needed
Cheap on fuel and super quiet

[ArranP]

A genset would still make sense on an all electric populsion boat.

[Simi 60]

Originally Posted by ArranP

A genset would still make sense on an all electric populsion boat.

So would simply having a diesel engine and prop.

[Fuss]

Originally Posted by Simi 60

So would simply having a diesel engine and prop.

And there we have it, almost correct , just put the propshaft alt on like I mentioned earlier and you have gone a long way towards optimisation of all options, you in theory then need less solar.

[s/v Jedi]

Originally Posted by skipperpete

Dockhead’s observations regarding upwind performance and and solar arrays makes perfect sense to me, my own boat is affected by exactly this, but the OP has a Roberts 57 and this is a vessel that really can carry a genset and fuel comfortably. On the other hand it could just as easily be self sufficient electrically with that much deck and cabintop space for a really large solar array.

Ahoy skipperpete! Can you tell us how much solar you had and how it slowed you down? Also, when did you remove it and what do you have now?

[GrowleyMonster]

Originally Posted by ArranP

A genset would still make sense on an all electric populsion boat.

Indeed. When I had my electric boat I often took my little Ryobi portable gasoline generator with me. It was emergency get'home power, not for routine charging. I did test it, though, and first I did it full manual, with a 2kw Variac and welding machine rectifier to convert 120VAC to what was needed by my 48v propulsion bank, which varied of course depending on state of charge and load. This requires careful monitoring, of course. I had two chargers aboard, a big heavy "dumb" charger that charged the entire bank on one output circuit, and a "smart" charger (It wasn't really all that smart!) that charged via four independent 12v output circuits, each connected to two of the 6v batteries. I tried both chargers and never made the generator breaker trip. So, a jug of gasoline and my lunchbox generator went along with me many times, though I never actually needed it. It was there in case.

Different use profiles, different equipment and methods. That little boat, I would never have permanently installed a proper diesel genset, although an entire diesel parallel hybrid system might have been nice. On a bigger or more valuable boat where the cost of a diesel is not a case of the tail wagging the dog, then an intelligently sized installed diesel genset does indeed make sense for an electric boat, and might even be regarded as a necessity, again, depending on the user and how he uses the boat.

[GrowleyMonster]

Originally Posted by Simi 60

So would simply having a diesel engine and prop.

Not to mention having both.

Depends on the boat and the user. There is no one size fits all. No way in hell I would install a diesel on a boat only used for racing on Lake Pontchartrain, or day sailing, for instance. EP costs a third of what a diesel costs, including batteries, and shore power is cheaper than diesel fuel, and will never make a sheen on the water from a careless mistake or a leaky tank or hose, and I never have to smell fuel. For a cruising motorboat, whole different pair a dime.

[malbert73]

My genset contributes so little to fuel burn- a season maybe is 100 hours and 30 gallons of diesel. Where I primarily boat- east coast of US- there are so many fuel guzzling powerboats and such a powerful industry that I’m not worried about either my footprint- nor scarcity of fuel. And solar panels and lithium batteries are not without environmental impact—

First to come will be rising fuel prices which I would welcome as it would make the huge “McMansion” power yachts into dock queens. Doubling fuel prices would still barely be a dent in my annual budget - which due to the excellent sailing ability of my boat- is less than 100 gallons of diesel between main and genset. That’s for 1500-2000 nm per season.
That’s a 2 hour day trip for a large power yacht

[Simi 60]

Originally Posted by malbert73

—

First to come will be rising fuel prices which I would welcome as it would make the huge “McMansion” power yachts into dock queens. Doubling fuel prices would still barely be a dent in my annual budget - which due to the excellent sailing ability of my boat- is less than 100 gallons of diesel between main and genset. That’s for 1500-2000 nm per season.
That’s a 2 hour day trip for a large power yacht

Can't really compare you're 40 ft to a couple of hundred ft of luxury super yacht
Also consider that they have several full time staff on board, I daresay fuel is a small part of the overall bill.

[malbert73]

Originally Posted by Simi 60

Can't really compare you're 40 ft to a couple of hundred ft of luxury super yacht

Also consider that they have several full time staff on board, I daresay fuel is a small part of the overall bill.

Correct. My point is a response to the upthread reasoning of lack of fuel supply in the future as a reason to ditch a genset.

I actually didn’t mean the crewed yachts- relatively few in number overall- but instead the proliferation of the new privately owned/operated McMansion yachts in the 50-60 foot range that plow along at 18 knots displacing tons of water per second, all fueled by massive amounts of diesel.

Our fuel needs, and footprint- the same as most cruising sailboats- is a drop in the bucket relative to the marine pleasure boat sector. So, the choice to go all renewables, or hybrid maintaining a genset- is very personalized to individual needs and desires. It will be decades before there isn’t fuel to be had- and first the private power yacht market has to collapse, as there is no earthly way electric drive will meet their use profile (>50gph for cruising speed).

Just saw another load of them being delivered to Baltimore from Europe last week

[FlyingScot]

Originally Posted by pwillems

I have always read that the purpose behind installing a standalone genset rather than just using the main engine to charge batteries is due to the inefficiencies of running a diesel engine with only the light load from the alternator. This makes sense, and I would agree. But, these days, it is quite easy to get hold of some very large alternators and very large inverters, so I am not sure it always makes all that much sense anymore.

Let's say a small catamaran owner has 2 * 20hp and a decent lithium bank that will happily accept high charge rates. A 400amp/12v alternator uses ~16hp (1 hp per 25 amps). At the full 400 amps output, that engine is at over 75% working load. Taking into account heat derating and other inefficiencies, the engine is still getting a pretty good workout for the entire duration of the charge.

Of course, you wouldn't want that alternator putting out its full charge when you actually need that engine to push the boat into some challenging seas, but that is easily managed with a clever regulator, or even a potentiometer if required.

Some things that have been mentioned that I don't believe are gathering enough attention.
- Power Take Off (PTO) rating of the engine. I'd be very shocked if you can find a PTO rating above 3-4 HP for a 20HP engine as rated from the manufacturer of the engine. Remember this is the load on the engine, not the output of the alternator.
- 400A @ 12V is practically unheard of. 2 x 200A is more likely but how do you find the room to mount them?
- Alternators are 50-65% efficient. So 400A becomes much more of a load on the engine.

I recommend installing as much solar as possible. A full width arch of bifacials made of high quality parts (panels, controllers, wiring, etc.).

Supplement your needs with one large alternator per engine. This is plan B and C.

Have a small generator as plan D.

Our system is:
Plan A: 2895wp of solar. 7 x MPPT. Ancor wiring, Blue Sea bus bars, 1320Ah of Victron LiFePO4.
Plan B & C: One Balmar XT170 per engine. Wakespeed controllers. Charging through Argofet isolators.
Plan D: We downgraded from Honda Eu2200i to Eu1000i. Charging either through 2 x Multiplus and or single 50A charger.

[Simi 60]

Originally Posted by malbert73

Correct. My point is a response to the upthread reasoning of lack of fuel supply in the future as a reason to ditch a genset.

I actually didn’t mean the crewed yachts- relatively few in number overall- but instead the proliferation of the new privately owned/operated McMansion yachts in the 50-60 foot range that plow along at 18 knots displacing tons of water per second, all fueled by massive amounts of diesel.

Don't like them either
Terribly inefficient use of resources in my eyes and I have a tough time understanding why anyone who actually knows boats or wants to be at one with nature would go that way.

Our fuel needs, and footprint- the same as most cruising sailboats- is a drop in the bucket relative to the marine pleasure boat sector. So, the choice to go all renewables, or hybrid maintaining a genset- is very personalized to individual needs and desires. It will be decades before there isn’t fuel to be had- and first the private power yacht market has to collapse, as there is no earthly way electric drive will meet their use profile (>50gph for cruising speed).

Our vessel is a recycled prawn trawler on her second life so pretty green in my eyes.
Large solar array means minimum Genset use, in summer we don't use it and are at 100% by midday.
We have spent a month in a marina now, first time in 7 years and still haven't plugged into shore power.

And instead of 50gph we use less than 4gph at cruise.
Not bad for 60 ft and 60 tonne
Some of the most fuel efficient powercats out there are only marginally better for a far greater capital outlay.

as there is no earthly way electric drive will meet their use profile

Still not there even if aiming at our 7.5 knot cruise.

Silent yachts cost several millions of dollars
Can only run all electric if running around 3 knots which would be painful even by sailing mono standards
And if needing better speed need to run 200hp gensets to keep up with demand.

Could have put shaft drive 100hp/side in, saved a million or more and had several lifetimes of diesel dollars earning interest in the bank.
Probably never need to touch the principle.

[akopac]

Originally Posted by s/v Jedi

I bet you are cheating with propane or other additional fuels

I do have a propane stove. I was really really good with heat transfer and thermal dynamics in college though and detailed the hell out of the box construction. It paid off…

[NYSail]

Originally Posted by deltaten

At the exorbitant $$ outlets get for new diesel gensets, I'd go with the Honda portable..or two, mebbe even a larger model. Not to run the whole boat, mind you; but as back-up charging for those times sun or runs are short.
You could buy 8-10 Hondas for the cost of a new inboard diesel
They sip fuel! A gallon or two of gas, stored and vented safely/properly could last quite a while.
Noise is minimal and a bit of sound shielding helps too. Just don't be a d!@k about running it .

There are alternatives to the $1200 (MSRP!) Honda 2200w, too. A quick poke around RV sites revealed quite a few comparisons. Honda also makes portable; but large-ish diesel gensets, in the same price range as NL and others. With all the troubles folks seem to have with "marine" gennies, if I needed all that power, it's the way I'd go.
HTH

I bought a 3.5kw genset 2 years ago. Great investment.I use it for hot water and a/c or heat. Batteries stay charged via solar so not issue but when I have it on I do load it up and top everything off. Unit is tapped into my diesel tank and burns .2 / .3 gallons an hour. No need to carry gasoline. We stay on hook/mooring full time. I installed it myself at a total cost of under 8,000. Everyone is different. For what wife and I do it was a bargain.
Had a Honda prior and they are great. Just a haste to get out and put back…. Worry about rain. And a single unit won’t run both ac units and make hot water. And while quiet they are loud compared with the genset. Don’t have the room for more than 1 to keep moving back and forth. And the gas storage for me was a pain.

Greg